<?php
/* 
 * Copyright (c) 2011 Antoine d'Otreppe de Bouvette
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

abstract class StatePattern {
    private static $classes = array();
    private $value;
    
    public static function switchState($stateName) {
        $class = get_called_class();
        
        if (!array_key_exists($class, self::$classes)) {
            self::$classes[$class] = array();
        }
        
        $states = &self::$classes[$class];
        
        if (array_key_exists($stateName, $states)) {
        }
        else {
            $stateClass = get_called_class() . '_' . $stateName;
            if (class_exists($stateClass)) {
                if (get_parent_class($stateClass) === $class) {
                    $states[$stateName] = new $stateClass($stateName);
                }
                else {
                    throw new RuntimeException(
                            "$stateClass does not extend $class.");
                }
            }
            else {
                throw new RuntimeException(
                        "No such state: $class::$stateName");
            }
        }
        
        return $states[$stateName];
    }
    
    public function __construct($value) {
        $this->value = (string) $value;
    }
    
    public function __toString() {
        return $this->value;
    }
}
